1. Field of the Invention
The invention relates in general to an electronic device and an antenna module thereof, and more particularly to an electronic device having a shielding casing and an antenna module thereof.
2. Description of the Related Art
Wireless communication, not subjected to the restriction of place nor requiring cable, has high mobility and has been widely used in various electronic devices. With regard to wireless communication technology, the design of antenna module places a very important role.
Referring to FIG. 1, a perspective of a conventional notebook computer 900 and an antenna module 920 is shown. The notebook computer 900 includes a host 930 and a display panel 940. As the structure of the notebook computer 900 is so complicated, the notebook computer 900 is susceptible to electromagnetic interference which occurs between internal electronic elements or due to external noises. To prevent the electronic elements of the notebook computer 900 from being affected by the above electromagnetic interference, a shielding casing 950 is used for covering the electronic elements.
However, the shielding casing 950 also shields the radiation of the antenna module 920, and becomes a barrier to the antenna module 920. Thus, the disposition of the antenna module 920 must avoid the shielding casing 950.
Referring to FIG. 2, FIGS. 3A˜3K, FIGS. 4A˜4K and FIGS. 5A˜5K. FIG. 2 is a return loss vs. frequency curve diagram of the antenna module 920 of FIG. 1. FIGS. 3A˜3K are diagrams of far-field power distribution of the antenna module 920 of FIG. 1 on X-Y plane. FIGS. 4A˜4K are diagrams of far-field power distribution of the antenna module 920 of FIG. 1 on Y-Z plane. FIGS. 5A˜5K are diagrams of far-field power distribution of the antenna module 920 of FIG. 1 on Z-X plane. According to the experimental results, the return loss, the radiation efficiency, the peak gain and the average gain at each frequency band are respectively shown in Table 1.1˜Table 1.6.
TABLE 1.1Return LossFrequency Band (GHz)2.42.55.155.875Measurement Result17.0113.4211.0812.27
As indicated in Table 1.1, when the antenna module 920 is at the frequency width of 2.4 GHz, 2.5 GHz, 5.15 GHz and 5.875 GHz, the return loss has a maximum value of 17.014 dBi and a minimum of 11.083 dBi, and the difference between the maximum return loss and the minimum return loss is 5.931 dBi. The experiment results show that the antenna module 920, despite having avoided the shielding casing 950, is still affected by the shielding casing 950 and has an over-diversified distribution of return loss at different frequency bands.
TABLE 1.2Radiation EfficiencyFrequencyRadiation Efficiency2.400 GHz59.432.450 GHz57.232.500 GHz55.935.150 GHz32.745.250 GHz42.905.350 GHz64.315.470 GHz58.695.600 GHz51.225.725 GHz56.475.825 GHz49.345.850 GHz43.19
As indicated in Table 1.2, of the 11 points measured when the antenna module 120 is at the frequency band of 2.4 GHz˜5.85 GHz, the radiation efficiency has a maximum value of 64.31% and a minimum value of 32.74%, and the difference between the maximum and the minimum radiation efficiency is 31.57%. For ordinary radiation efficiency, the acceptable minimum level is 45%. However, in the above frequency bands, there are three frequency bands (5.15 GHz, 5.25 GHz and 5.85 GHz) whose radiation efficiencies are lower than the minimum level. The experiment results show that the antenna module 920, despite having avoided the shielding casing 950, is still affected by the shielding casing 950 and has an over-diversified distribution of radiation frequency at different frequency bands and too many frequency bands are below the minimum radiation frequency.
TABLE 1.3Peak Gain (dBi)Frequency Band (GHz)2.42.452.55.155.255.35X-Y4.734.404.072.843.823.60Y-ZZ-X
TABLE 1.4Peak Gain (dBi)Frequency Band (GHz)5.475.65.7255.8255.85X-Y3.905.097.317.626.89Y-ZZ-X
As indicated in Table 1.3˜1.4, of the 11 points measured when the antenna module 120 is at the frequency band of 2.4 GHz˜5.85 GHz, the peakgain has a maximum value of 7.62 dBi and a minimum value of 2.84 dBi, and the difference between the maximum and the minimum peak gain is 4.78 dBi. The experiment results show that the antenna module 920, despite having avoided the shielding casing 950, is still affected by the shielding casing 950 and has an over-diversified distribution of peak gain at different frequency bands.
TABLE 1.5Average Gain (dBi)Frequency Band (GHz)2.42.452.55.155.25X-Y−4.54−4.50−4.26−7.00−5.43Y-Z−3.62−3.92−3.89−6.14−3.50Z-X−2.37−2.50−2.62−5.30−3.88
TABLE 1.6Average Gain (dBi)Frequency Band (GHz)5.355.475.65.7255.8255.85X-Y−4.31−3.96−4.51−4.76−5.44−5.93Y-Z−3.01−2.63−3.09−2.78−4.11−4.48Z-X−2.94−2.07−2.09−2.16−2.51−3.04
As indicated in Table 1.5˜1.6, of the 11 X-Y plane points measured when the antenna module 120 is at the frequency band of 2.4 GHz˜5.85 GHz, the average gain has a maximum value of −7.00 dBi and a minimum value of −3.96 dBi, and the difference between the maximum and the minimum average gain is 3.04 dBi. The experiment results show that the antenna module 920, despite having avoided the shielding casing 950, is still affected by the shielding casing 950 and has an over-diversified distribution of average gain at different frequency bands.
During the design of the antenna module 920, the antenna module 920 must go through serial tests to find out the most suitable position of disposition. However, despite the antenna module 920 is disposed at the most suitable position, the antenna module 920 is still affected by the shielding casing 950. In order to avoid the antenna module 920 being affected by the shielding casing 950, the antenna module 920 may even be disposed at a position with poor direction of frequency radiation. Thus, how to develop an electronic device and an antenna module capable of enhancing signal radiation has become an imminent issue to be resolved.